1. Field
Exemplary embodiments of the present invention relate to a light emitting diode chip and a method of fabricating the same, and to a light emitting diode chip having a distributed Bragg reflector and a method of fabricating the same.
2. Discussion of the Background
A gallium nitride-based light emitting diode chip emitting blue or ultraviolet wavelength light may be used for various applications. In particular, various types of light emitting diode packages emitting mixed color light, for example, white light required for a backlight unit, general lighting, or the like, have been marketed.
Since the light output from the light emitting diode package may depend on the light emission efficiency of the light emitting diode chip, research to improve the light emission efficiency of the light emitting diode chip has been continuously conducted. In particular, attempts to improve the light extraction efficiency of the light emitting diode chip have been performed. For example, technology of forming a metal reflector or a distributed Bragg reflector (DBR) on a bottom surface of a transparent substrate such as a sapphire substrate has been researched.
FIG. 1 shows reflectivity measured by forming an aluminum layer on the bottom surface of a sapphire substrate according to the related art.
It can be appreciated from FIG. 1 that in the case of the sapphire substrate on which the aluminum layer is not formed, reflectivity of about 20% is shown, but in the case of the sapphire substrate on which the aluminum layer is formed, reflectivity of about 80% is shown over a visible wavelength range.
FIG. 2 shows the reflectivity measured by the DBR formed by periodically applying TiO2/SiO2 to the bottom surface of the sapphire substrate according to the related art.
As shown in FIG. 2, when the DBR is formed to reflect light emitted from the light emitting diode chip, for example, emitted light having a peak wavelength of 460 nm. FIG. 2 shows that reflectivity in the light emitting diode using the DBR may reach approximately 100% in a blue wavelength range, for example, a wavelength range of 400 to 500 nm.
However, the DBR can only increase the reflectivity for a part of the visible range. Therefore, the reflectivity for other ranges is considerably lower than that shown in FIG. 2 for the wavelength range of 400 nm to 500 nm. That is, as shown in FIG. 2, the reflectivity for a wavelength of about 520 nm or more is suddenly reduced while most of the reflectivity is less than 50% at a wavelength of 550 nm or more.
Therefore, when mounting the light emitting diode chip using the DBR in a light emitting diode package to emit white light, the DBR shows high reflectivity for light of the blue wavelength range emitted from the light emitting diode chip but the DBR does not show efficient reflection characteristics for light emitted in the green and/or red wavelength ranges. Therefore, there is a limit in improving the light emission efficiency of the light emitting diode package.
Meanwhile, attempts have been made to apply the DBR to the reflecting surface of the light emitting diode package, which have not been achieved due to a limitation of the DBR deposition technology. For example, there have been problems with a deposition temperature, a plasma temperature, and the like.